In many energy generation and chemical processing plants, there is a need to dissipate excess heat from a liquid and, in particular, from excessively heated water. One widely used technique for dissipating such excess heat is through the use of a cooling tower wherein the heated liquid, usually water, is sprayed into an upper portion of the cooling tower and allowed to traverse the vertical length of the tower while a gas, usually air, is also circulated through the cooling tower whereby the contact between the water and the air induces a heat and mass transfer such that heat and vapor from the water are carried away with the exhaust air exiting the cooling tower.
A key factor in designing cooling towers for obtaining efficient heat and mass transfer is to provide a large surface area that is continually wetted by, for example, water and over which a gas (e.g., air) can continually circulate. To provide such large surface areas, packings (also denoted structured packings) are used wherein each such packing has a plurality of interleaved channels that provide liquid and gas communication vertically through the packing. The channels provide most of the surface area by which the liquid and gas come in contact to increase the heat and mass transfer. In one typical configuration, one or more packings span a cross section of the interior of a cooling tower such that: (a) the liquid inlet is above the packing thereby allowing the liquid to be cooled to fall onto the packing and traverse the packing channels in flows having large exposed surface areas, and (b) concurrently with (a), a gas, typically air, is drawn upwardly from beneath the packing through the packing channels thereby cooling the liquid within the packing by evaporation as the air moves counter to the flow of the liquid.
The design or structure of a packing for a cooling tower has heretofore been determined solely by packing designer's experience together with trial and error. That is, packing designers familiar with the results obtained from packings used in previously built cooling towers have heretofore made educated guesses as to an acceptable packing design for a new cooling tower. However, there are a large number of factors which may significantly affect the effectiveness of the packing and thus the performance of the cooling tower, for example, the ambient temperature and humidity of the cooling tower site, the air and water flow rates through the cooling tower, the water inlet temperature and the geometry of the channels through the packing itself. Thus, without an understanding of the fundamental physics of heat and mass transfer within the proposed packing designs, packing designers have resorted to trial and error to determine which educated guess for a packing design performs satisfactorily given the cooling tower and site characteristics.
The above described packing design methodology has the following disadvantages:
(a) the determination of an optimal or near optimal packing design can be cost and/or time prohibitive in that substantial time and resources can be expended in constructing, installing and testing each candidate packing design; and PA1 (b) advancement in packing design has been inhibited in that there is no tool allowing easy simulation of cooling tower performance with different packing designs.
Thus, it would be advantageous to have a cooling tower simulation tool to predict the performance of the cooling tower according to input packing geometric characteristics. More precisely, it would be advantageous to have a simulation tool which uses the environmental characteristics of the cooling tower site, cooling tower performance constraints as well as the geometric characteristics of the packing for predicting the performance of the packing in facilitating heat and mass transfer between a liquid and gas and more particularly between water and air.